Institute for Molecular Bioscience and School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia.
Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ.
Mol Biol Evol. 2018 Jul 1;35(7):1706-1711. doi: 10.1093/molbev/msy061.
Sacoglossan sea slugs offer fascinating systems to study the onset and persistence of algal-plastid symbioses. Elysia chlorotica is particularly noteworthy because it can survive for months, relying solely on energy produced by ingested plastids of the stramenopile alga Vaucheria litorea that are sequestered in cells lining its digestive diverticula. How this animal can maintain the actively photosynthesizing organelles without replenishment of proteins from the lost algal nucleus remains unknown. Here, we used RNA-Seq analysis to test the idea that plastid sequestration leaves a significant signature on host gene expression during E. chlorotica development. Our results support this hypothesis and show that upon exposure to and ingestion of V. litorea plastids, genes involved in microbe-associated molecular patterns and oxidative stress-response mechanisms are significantly up-regulated. Interestingly, our results with E. chlorotica mirror those found with corals that maintain dinoflagellates as intact cells in symbiosomes, suggesting parallels between these animal-algal symbiotic interactions.
食藻螺类海蛞蝓为研究藻类-叶绿体共生的起始和持续提供了引人入胜的系统。Elysia chlorotica 尤为引人注目，因为它可以在仅依靠摄入的 Vaucheria litorea 绿藻叶绿体产生的能量的情况下存活数月，这些叶绿体被隔离在其消化憩室的细胞内。这种动物如何在没有藻类细胞核丢失的蛋白质补充的情况下维持活跃的光合作用细胞器仍然未知。在这里，我们使用 RNA-Seq 分析来检验这样一种观点，即叶绿体隔离在 E. chlorotica 发育过程中对宿主基因表达留下显著的特征。我们的结果支持这一假设，并表明在暴露于并摄入 V. litorea 叶绿体后，与微生物相关的分子模式和氧化应激反应机制相关的基因显著上调。有趣的是，我们在 E. chlorotica 中的结果与那些在珊瑚中发现的结果相似，珊瑚将虫黄藻作为完整细胞保存在共生体中，这表明这些动物-藻类共生相互作用之间存在相似之处。
